1. Field of the Invention
The present invention relates to the preparation of flexible copolyamides having improved mechanical properties, high molecular weights and high melting points.
2. Description of the Prior Art
For certain plastics applications, it is necessary to have polymers which possess the characteristics of, on the one hand, the chemical resistance of the polyamides, while, on the other, having a greater flexibility than that of the conventional polyamides, such as polyhexamethylene adipamide or polycaprolactam.
The use of a plasticizer makes it possible to obtain flexibility, but this is generally to the detriment of the chemical stability, or the other mechanical properties. The use of copolyamides has also been proposed. Contrariwise, numerous copolyamides which possess a high flexibility, such as copolyamides based on caprolactam, hexamethylenediamine and adipic and sebacic acids, exhibit a high sensitivity to the action of solvents and, in particular, of water. Other copolyamides, which combine flexibility with a good resistance to water, too have been proposed. Examples which may be mentioned are the copolyamides described in U.S. Pat. No. 3,240,732 or French Pat. No. 1,395,076.
However, these prior art copolyamides do not possess adequate mechanical characteristics such as to find use in place of the conventional polyamides.